1. Field of the Art to Which the Invention Pertains
The present invention relates to a gas generator for an air bag that protects a driver or a passenger from an impact, and more particularly to a gas generator capable of adjusting the amount of a supply gas in accordance with the circumstances.
2. Prior Art
For the purpose of protecting a driver or a passenger from an impact of a vehicle collision, a vehicle is equipped with an air bag device. The air bag device includes a sensor, a control unit, a gas generator, an air bag, etc. The gas generator includes an ignition unit and a gas generating material.
Upon detection of an impact by the sensor, a detection signal is supplied to the control unit which conducts arithmetic calculation in response to the detection signal. The control unit generates an output signal representative of the result of the arithmetic calculation to the ignition unit of the gas generator. The ignition unit is thus operated. With this operation, the gas generating material is burned to generate a gas having a high temperature and a high pressure. The gas is injected into the air bag (bag body) from a diffuser of the gas generator. As a result, the air bag is inflated to form a cushion that absorbs an impact between a solid structure and the driver or the passenger.
In a conventional gas generator for an air bag device, the capacity of an air bag, the amount of gas generating material, and so on are determined such that an optimum inflation rate of the air bag, an optimum internal pressure in the air bag, etc., are obtained on the presumption of a certain standard condition. However, there may occur a case where a preset condition is changed depending on a vehicle velocity, a vehicle room temperature, a physique of a driver or a passenger, a sitting posture of the driver or the passenger, whether the driver or the passenger is being restrained by a seat belt or not, and so on at the time of operating the air bag device. In such a situation, with a certain standard amount of a supply gas, the optimum inflation rate of the air bag, the optimum internal pressure in the air bag, and so on cannot be obtained.
The object of the present invention is to provide a gas generator for an air bag which is capable of adjusting the amount of a supply of gas in accordance with the circumstances.
The gas generator for an air bag, according to the present invention, includes: an outer shell vessel having a pressurized gas accommodating chamber for storing a gas therein, and a diffuser nozzle, provided at a opening of the outer shell vessel, having gas discharge ports in communication with the air bag, the opening being covered by a first rupturable partition member;
ignition means disposed within the outer shell vessel and operates upon receiving an operation signal; and
gas generating means for generating gas when the ignition means operates, wherein
the outer shell vessel includes a gas discharge chamber attached thereto at a position isolated from the diffuser nozzle, and provided over a second rupturable partition member, the gas discharge chamber including a gas discharge port that communicates an inner space thereof with an atmosphere, and
the gas discharge chamber having a gas discharge member that ruptures the second partition member to discharge gas upon receiving another operation signal.
It is preferable that the second partition member is formed of a rupturable gas sealing plate that seals the second opening.
Also, it is preferable that the second partition member has a rupturable tube-shaped body that protrudes into the gas discharge chamber. A notch groove may be formed in the outer periphery of the tube-shaped body.
The gas generating means can mainly be made of any one of a solid gas generating agent, pressurized gas, and a liquid which is gasified by heating.
Also, the gas discharge means can be provided with a piston member which ruptures the partition member.
The piston member may have a sharp tip or a flat tip.
The gas discharge means can be formed of an electric ignition unit.
In the gas generator of the present invention, the second partition member isolates the pressurized gas accommodation chamber of the outer shell vessel from the gas discharge chamber. The gas discharge member operates upon receiving an operating signal to rupture the partition member. In this situation, a part of the pressurized gas enters the gas discharge chamber, through the ruptured opening, and then discharges from the discharge port of the gas discharge chamber to the atmosphere. When the gas discharge means is inoperative, the entire amount of the generated gas is provided to the air bag. In this way, the gas generator of the present invention can adjust the amount of supply gas according to the circumstances. The operating signal can be obtained from the control means in the air bag device containing the gas generator of the present invention therein. The control means inputs detection signals from a variety of sensors such as a vehicle velocity sensor, a temperature sensor that detects the vehicle room temperature, a displacement sensor for detecting a physique of a driver or a passenger, a sitting posture of the driver or the passenger, etc., to arithmetically calculate the detection signal, thus outputting a signal representative of the arithmetical calculation result.
As described in the foregoing, the present invention realizes a gas generator that can adjust the gas supply amount in accordance with the situation. Namely, the gas generator discharges a part of the gas, by activating the gas discharge member, to optimize internal pressure of the air bag.